La Nina

La Niña is over

May 3rd, 2012 at 2:05 pm by under Weather

See related story here on KXAN News Page

Synopsis: La Niña has transitioned to ENSO-neutral conditions, which are expected to continue through northern summer 2012.

La Niña dissipated during April 2012, as below-average SSTs weakened across most of the equatorial Pacific Ocean and above-average SSTs persisted in the east (Fig. 1). The Niño 4 and Niño 3.4 indices were warmer than -0.5oC throughout the month, and the Niño 3 and Niño 1+2 indices remained positive (Fig. 2). The oceanic heat content (average temperature in the upper 300m of the ocean) anomalies also became positive in April (Fig. 3), as below-average sub-surface temperatures largely disappeared and above-average sub-surface temperatures expanded in both the central and eastern Pacific (Fig. 4). Consistent with the demise of La Niña, enhanced trade winds and reduced convection over the central equatorial Pacific were much weakened during April, and the area of enhanced convection that had previously dominated the western Pacific and Indonesia became disorganized (Fig. 5). Collectively, these oceanic and atmospheric patterns indicate a transition from La Niña to ENSO-neutral conditions. (more…)


La Niña is Back for the Winter

November 7th, 2011 at 1:30 pm by under Weather

There is no doubt the La Niña has returned. Check out the Pacific Ocean temperature anomalies in this image from NOAA’s Environmental Visualization Laboratory.

 

A sea surface anomaly, or departure from the average temperature, is calculated by subtracting the temperatures from a time period of interest from the 30-year average (1981-2010) for the same time period. The resulting data shows areas that are hotter or colder than normal. Sea surface temperature anomaly data allow scientists to quickly identify features of interest, especially for El Niño/La Niña, coastal upwelling, and hurricane intensification.

The strengthening La Niña in the Pacific Ocean brings with it a host of possible trends as outlined by the NOAA Climate Prediction Center’s Seasonal Outlook released October 20, 2011. These trends include lower than normal precipitation for the southwest and southern Great Plains and Mississippi Valley. Below normal temperatures are favored for southern sections of the Florida peninsula, northern Great Plains and northern Rockies. Trends favor modest warmer than normal conditions for much of the east.

Unfortunately for Central Texas and most of the state, this means a continuation of our historic drought into 2012.

This imagery uses the Optimum Interpolation SST (commonly called OI SST) anomaly dataset generated by NOAA’s National Climatic Data Center. OI SST uses infrared and microwave data from polar-orbiting satellites (NOAA AVHRR; NASA AMSR-E, a previous contributor operating onboard the AQUA satellite, ceased operation October 4, 2011) and oceanic buoys to calculate one of the most accurate analyses of sea surface temperature.

Related Information:NOAA/NCDC OI SST products page

(Content from NOAA)


La Niña weakening, but may persist through spring

February 21st, 2011 at 3:15 pm by under Weather

Our monthly La Niña update from the Climate Prediction Center indicates a weakening phase has begun, but the cooler-than-average Pacific water temperatures will likely remain an influence in our weather into, and possibly through spring.  Most notably, below average rainfall is expected across Texas, which will worsen our ongoing drought conditions.

http://www.cpc.ncep.noaa.gov/products/hurricane/sstanim.gif

EL NIÑO/SOUTHERN OSCILLATION (ENSO)
DIAGNOSTIC DISCUSSION
issued by
CLIMATE PREDICTION CENTER/NCEP
10 February 2011
ENSO Alert System Status: La Niña Advisory
Spanish Version
Synopsis: ENSO-Neutral or La Niña conditions are equally likely during May-June 2011

La Niña persisted during January 2011 as reflected by well below-average sea surface temperatures (SSTs) across much of the equatorial Pacific Ocean (Fig. 1). However, some weakening was evident in certain atmospheric and oceanic anomalies, in part due to Madden-Julian Oscillation activity. Most Niño indices were between –1oC and –1.5oC at the end of January, with the easternmost Niño-1+2 region returning to near-average (Fig. 2). A lessening of the negative subsurface oceanic heat content anomalies (average temperatures in the upper 300m of the ocean, Fig. 3) was observed mostly in association with an eastward shift in the above-average temperatures at depth in the central equatorial Pacific (Fig. 4). Convection remained enhanced over Indonesia and suppressed over the western and central equatorial Pacific (Fig. 5). Also over the western and central equatorial Pacific, the anomalous low-level easterly and upper-level westerly winds decreased in magnitude. Collectively, these oceanic and atmospheric anomalies reflect an ongoing, mature La Niña that has begun to weaken.

Nearly all of the ENSO model forecasts weaken La Niña in the coming months (Fig. 6). A majority of the models predict a return to ENSO-neutral conditions by May-June-July 2011, although some models persist a weaker La Niña into the Northern Hemisphere summer 2011. Recent trends in the observations and models do not offer many hints on which outcome is more likely. Also, model skill is historically at a minimum during the Northern Hemisphere spring (the “spring barrier”). Therefore La Niña is expected to weaken during the next several months, with ENSO-neutral or La Niña conditions equally likely during May-June 2011.

Expected La Niña impacts during February-April 2011 include suppressed convection over the west-central tropical Pacific Ocean, and enhanced convection over Indonesia. Potential impacts in the United States include an enhanced chance of above-average precipitation in the Northern Rockies and western regions of the Northern Plains (along with a concomitant increase in snowfall), Great Lakes, and Ohio Valley. Below-average precipitation is favored across much of the southern states. An increased chance of below-average temperatures is predicted for much of the West Coast and northern tier of states (excluding New England), and a higher possibility of above-average temperatures is forecast for much of the southern and central U.S. (see 3-month seasonal outlook released on January 20th, 2011).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts for the evolution of El Niño/La Niña are updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 10 March 2011. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: ncep.list.enso-update@noaa.gov.

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service

La Nina Believed to be Forming

June 3rd, 2010 at 4:21 pm by under Weather

 

While the rainfall since yesterday has been a welcome change, don’t get used to it.  In an ominous sign from the Climate Prediction Center today, experts say they are interpreting the current cooling of some areas of the Pacific Ocean to be a sign that a La Nina is in the process of developing, and should fully form over the summer. 

La Nina episodes are normally responsible for bringing drier than average weather to Texas. A persistent La Nina period helped create our area’s record breaking drought between 2007-2009.  In other words, our next drought may be beginning now.

EL NIÑO/SOUTHERN OSCILLATION (ENSO)
DIAGNOSTIC DISCUSSION
issued by
CLIMATE PREDICTION CENTER/NCEP
3 June 2010
 
ENSO Alert System Status: La Niña Watch / Final El Niño Advisory
 
 
Spanish Version
 
Synopsis: Conditions are favorable for a transition to La Niña conditions during June – August 2010.El Niño dissipated during May 2010 as positive surface temperature (SST) anomalies decreased rapidly across the equatorial Pacific Ocean and negative SST anomalies emerged across the eastern half of the Pacific (Fig. 1). All of the Niño indices decreased between 0.5oC to 1.0oC during the month (Fig. 2). Since the end of February, subsurface heat content anomalies (average temperatures in the upper 300m of the ocean, Fig. 3) have decreased steadily. Below-average temperatures have strengthened at depth and currently extend to the surface in parts of the eastern Pacific (Fig. 4). Also during May, enhanced convection persisted over Indonesia, while the area of suppressed convection strengthened and expanded over the tropical central Pacific (Fig. 5). The low-level easterly trade winds strengthened over the western and central equatorial Pacific, and anomalous upper-level westerly winds prevailed over the east-central Pacific. Collectively, these oceanic and atmospheric anomalies reflect the demise of El Niño and return of ENSO-neutral conditions.The majority of models predict ENSO-neutral conditions (between -0.5oC to +0.5oC in the Niño-3.4 region) through early 2011 (Fig. 6). However, over the last several months, a growing number of models, including the NCEP Climate Forecast System (CFS), indicate the onset of La Niña conditions during June-August 2010. There is an increasing confidence in these colder model forecasts, which is supported by recent observations that show cooling trends in the Pacific Ocean and signs of coupling with the atmospheric circulation. Therefore, conditions are favorable for a transition to La Niña conditions during June-August 2010.This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts for the evolution of El Niño/La Niña are updated monthly in the Forecast Forumsection of CPC’s Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 8 July 2010. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: ncep.list.enso-update@noaa.gov.
 
Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
Camp Springs, MD 20746-4304

El Nino Dead – La Nina Looming?

May 20th, 2010 at 9:56 pm by under Weather

In today’s monthly update from the Climate Prediction Center, some mixed news for us as we head closer to summer. 

Climate forecasters are predicting drier than average weather in the 8-14 day period, which takes us into early June (see graphic below).  That would not be good news, as we have yet to see normal May rainfall.  Only one inch of rain has fallen so far this month at the airport, which is about two inches below average.

There is better news when looking at the CPC’s June outlook (below). Our Central Texas  region is in, or near the area forecast to receive above average rainfall during the month of June.

And, I don’t think anyone will complain about the temperature outlook below. Notice that nearly all of  Texas is forecast to be cooler than normal during June. Let’s hope that is right!

And while not quite as optimistic of an outlook for our area, notice below that parts of Central Texas are in the region of the state forecast to experience a cooler-than-normal summer.

 In the graphics below, most of North Texas is expected to enjoy below average temperatures during the period June through August, but most of the state, except the upper Texas coast,  has an equal chance of being wetter or drier than normal.

Read the CPC’s climate discussions below, where they pronounce the end of the El Nino, and discuss increasing evidence that a La Nina episode may be returning this year.

     

PROGNOSTIC DISCUSSION FOR MONTHLY OUTLOOK
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD
830 AM EDT THU MAY 20 2010

30-DAY OUTLOOK DISCUSSION FOR JUNE 2010

SEA SURFACE TEMPERATURE (SST) ANOMALIES NEAR THE EQUATOR IN THE EAST CENTRAL
PACIFIC OCEAN HAVE DECREASED MARKEDLY IN THE PAST FEW WEEKS.  SSTS ARE NOW
SLIGHTLY BELOW NORMAL ALONG THE EQUATOR BETWEEN ABOUT 100 AND 160W LONGITUDE,
SUGGESTING AN END TO THE EL NINO CONDITIONS PRESENT FOR THE PAST YEAR OR SO.
SEVERAL

(more…)


El Nino Fading, La Nina Returning?

May 6th, 2010 at 2:31 pm by under Weather

The Climate Prediction Center’s monthly update today was a little discouraging.  We already knew the El Nino was fading away.  We owe our drought-breaking fall and winter rainfall to the pattern, so it’s hard to say goodbye, but that’s the nature of this cyclical pattern. 

One would hope that we would at least transition to a period of “neutral” or average Pacific Ocean water temperatures for the remainder of the year, which is likely. However, the CPC said today that a third of their climate models are predicting a quick transition to a La Nina pattern. 

That, of course, would be bad news for us, as much of the credit, or blame, for our record breaking two year drought was given to a persistent La Nina weather pattern.

EL NIÑO/SOUTHERN OSCILLATION (ENSO)
DIAGNOSTIC DISCUSSION
issued by
CLIMATE PREDICTION CENTER/NCEP
6 May 2010
 
ENSO Alert System Status: El Niño Advisory
 
 
Spanish Version
 
Synopsis: A transition to ENSO-neutral conditions is expected by June 2010, which will continue into the Northern Hemisphere summer 2010.El Niño weakened during April 2010 as positive surface temperature (SST) anomalies decreased across the equatorial Pacific Ocean. However, SST anomalies still exceeded +0.5oC across most of the Pacific at the end of the month (Fig. 1 and Fig. 2). Since the end of February, subsurface heat content anomalies (average temperatures in the upper 300m of the ocean, Fig. 3) have decreased steadily in association with the expansion and strengthening of below-average temperatures at depth (25-200m; Fig. 4). Also, enhanced convection developed over Indonesia, while suppressed convection strengthened and expanded over the tropical Pacific, south of the equator (Fig. 5). The low-level equatorial trade winds remained near-average, and anomalous upper-level westerly winds prevailed over the central Pacific during much of April. Collectively, these oceanic and atmospheric anomalies reflect a weakening El Niño.

Nearly all models predict decreasing SST anomalies in the Niño-3.4 region through the Northern Hemisphere summer 2010 (Fig. 6). Most models predict a transition to ENSO-neutral conditions during April-June 2010, followed by ENSO-neutral conditions through the end of the year. However, by July-September 2010, the envelope of model solutions includes a significant number (nearly a third) indicating the onset of La Niña conditions. Even though ENSO-neutral conditions are most likely during the second half of the year, the general tendency of the models in recent months has been toward increasingly negative SST anomalies in the Niño-3.4 region. These forecasts, in addition to various oceanic and atmospheric indicators, indicate a growing possibility of La Niña developing during the second half of 2010.

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts for the evolution of El Niño/La Niña are updated monthly in the Forecast Forumsection of CPC’s Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 10 June 2010. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: ncep.list.enso-update@noaa.gov.